Gas-exchange,photo-and antioxidant protection, and metal accumulation in I-214 and Eridano Populus sp. clones subjected toelevated zinc concentrations

Rooted cuttings of Eridano and I-214 Populus clones were treated in hydroponics with high [Zn] toestablish their phytoextraction capacity and physiological responses for phytoremediation. The Bio-concentration factor, Uptake ratio and Translocation factor revealed that the highest Zn accumulationoccurred in roots. Lower accumulation at 1 mM [Zn] in Eridano aerial parts limited Zn toxicity onphotosynthetic machinery. Increasing [Zn] negatively affected growth, net photosynthesis, stomatalconductance, maximum quantum yield, chlorophyll content and hydric parameters. The physiologicalimpairment in I-214 at 1 mM [Zn] indicated a greater sensitivity to high [Zn] than Eridano. At 5 mM [Zn],high toxicity for both clones occurred. Upregulation of photoprotective and antioxidant responses wasa consequence of Zn stress rather than a Zn tolerance mechanism. Increased de-epoxidation state of thexanthophyll-cycle, -Tocopherol and reduced glutathione and decreased total phenolics in I-214 at 1 mM[Zn] suggested that it responded earlier to oxidative stress when compared to Eridano.